Mercury Levels Same in Autistic, Other Children
Fish Consumption Predicted Levels Best, Researchers Found
Mercury Levels and Autism: Study Details continued...
The children were part of the Northern California-based Childhood Autism Risks from Genetics and the Environment (CHARGE) study, for which Hertz-Picciotto is the principal investigator. Children aged 24-60 months are enrolled in the study, in which researchers are looking at a variety of exposures and their possible association with the disorder. Some of the participants have autism spectrum disorders, some have other developmental disorders, and a third group of children is typically developing, serving as study controls.
Her team looked at a variety of sources of mercury in the environment, including consumption of fish, use of personal care products that contain mercury such as nasal sprays and earwax removal products, and vaccinations. They also looked at whether children had mercury-based dental amalgam fillings.
Mercury Levels: Study Findings
The autism group did not differ from the typically developing group in the level of mercury circulating in their blood after the researchers adjusted for the sources of mercury, Hertz-Picciotto says.
''There are no obvious differences in the circulating levels of mercury" among the three groups, she says.
"Unadjusted, those with autism had lower levels as it turns out," she says. That may be due to a lower consumption of fish among those with autism, she says, perhaps because of the tendency to be picky eaters and adhere to the same foods.
The average levels of mercury were 0.24 micrograms per liter for the typically developing children, 0.26 micrograms per liter for those with autism or autism spectrum disorder, and 0.16 micrograms for those with other developmental disorders, she found.
To put that in perspective, Hertz-Picciotto says the Environmental Protection Agency considers a level of 5.8 micrograms per liter not risky for pregnant women. There is no specific standard set for children, she says.
Mercury Levels and Autism: Other Opinions
The new study drew mixed reactions from experts. The new findings ''should be reassuring to parents," says Geraldine Dawson, PhD, chief science officer for Autism Speaks and a research professor at the University of North Carolina, Chapel Hill.
''There has been concern by some parents that just the normal kind of exposure to mercury in our environment ... might have a bigger effect on children with autism, and they might have specific trouble metabolizing mercury,” Dawson says.